# Which of the following compounds is/are polar covalent: H_2O, CaCl_2, N_2, CH_4, HNO_3? How is this determined?

And with ionic species, because the charges are formally SEPARATED, we generally do not speak of polarity. So for $C a C {l}_{2}$ we speak of an ionic salt.
On the other hand, for ""^(delta+)H-stackrel(delta-)O-H, ""^(delta+)H-stackrel(delta-)Ostackrel(+)N(=O)(-O^(-)) (the nitrogen is also formally quaternized), there is charge separation, polarity, and thus these are polar covalent molecules.
On the other, other hand, for ${N}_{2}$, and $C {H}_{4}$, there is NO polarity, no charge separation, and these species are classic non-polar molecules.